The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Known internal combustion engines may be configured with exhaust gas recirculation (EGR) systems to reduce emissions of nitrogen oxides (NOx) by reducing peak combustion temperatures within the engine cylinders during transient and steady-state operating conditions. Known EGR systems divert flow of a portion of exhaust gas into an intake system of the engine, and include a controllable EGR valve, an EGR cooling system including a heat exchanger, and suitable piping elements. Flow of the EGR gas in the direction of the intake system may be induced by a pressure differential between the intake and exhaust systems.
EGR cooling systems are susceptible to fouling, which can reduce thermal effectiveness of the EGR cooling system and controllability of the EGR valve. Fouling may be caused by precipitation of hydrocarbons and particulate matter onto a surface of the heat exchanger. Fouling of the EGR cooling system may result in reduced heat transfer from EGR gas and reduced EGR flow, thus affecting peak combustion temperatures and increasing NOx emissions. Precipitated hydrocarbons, particulate matter, and other exhaust elements may harden through aging and repetitive temperature cycles associated with engine shutdown and startup. Fouling of an EGR cooling system also affects mass flowrate of EGR gas and thermal performance of the EGR cooling system.